In the 3GPP Working Group “SA2”, discussion is made on positioning methods for the “Location Based Service”, which is a kind of a location information management service for a mobile station UE.
As such positioning methods, studied are the “C-plane based positioning” performed via a C-plane established between a mobile station UE and a GMLC (Gateway Mobile Location Center) sever, the “U-plane based positioning” performed via a U-plane established between a mobile station UE and an SUPL (Secure User Plane Location) sever, and the like, for example, as shown in FIGS. 10 and 11.
Additionally, concrete specifications of the “U-plane based positioning” using an SUPL sever as described above are formulated by the OMA (Open Mobile Alliance).
In the “U-plane based positioning”, a mobile station UE equipped with a GPS (Global Positioning System) positioning function is configured to report a GPS positioning result to an SUPL server via a U-plane established between itself and the SUPL server, and the SUPL server is configured to compute location information on the mobile station UE
Here, assumable examples of the “Location Based Service” include an emergency call service and a service for lawful interception by a police agency or the like.
Note that, in such a service, when the mobile station UE is unable to report location information itself on the mobile station UE, the mobile station UE is required to at least report a global cell ID of a radio base station eNB to which the mobile station UE is connected.
However, the “U-plane based positioning” using an SUPL server has a problem that the SUPL server cannot acquire a global cell ID of a cell under control of the radio base station eNB to which the mobile station UE is connected.
More specifically, in the “U-plane based positioning” using an SUPL server, the mobile station UE is only aware of an ID (a scrambling code) of a cell where the mobile station UE is “camped” on, or of a cell where the UE performs “idle-to-active” transition. For this reason, there is a problem that, if the mobile station UE moves, at the start of SUPL positioning, from a cell where the mobile station UE is previously “camped on” or from a cell where the UE performed “idle-to-active” transition, the mobile station UE is unable to inform, to the SUPL server, a global cell ID of a cell under control of a radio base station eNB to which the mobile station is currently connected.